Q49E - Organic Chemistry (Mcmurry)

Question

Treatment of an $\alpha , \beta$ -unsaturated ketone with basic aqueous hydrogen peroxide yields an epoxy ketone. The reaction is specific to unsaturated ketones; isolated alkene double bonds do not react. Propose a mechanism.

Step-by-Step Solution

Answer

Step 1: Epoxidation of alpha, beta-unsaturated ketones

Epoxidation of alpha and beta-unsaturated ketone is carried out by various reagents like hydrogen peroxide under very strong basic conditions.

Strong bases NaOH, KOH & K₂CO₃ are used.

Peroxide generally attacks the carbon-carbon double bond and epoxide form.

Step 2: Mechanism of the given reaction

In the given reaction first acidic hydrogen of hydrogen peroxide is abstract by the base and we get an anion O-O-H

In the next step, the anion form is attacked on the carbon-carbon double bond and we get epoxide on the $\alpha ,\beta$ unsaturated double bond as shown in the mechanism.